3.1 Gold Microtube
Membrane Preparation
(See Note 9)
1. Rinse the membrane sequentially in three 100 mL portions of
methanol, leaving the membrane in each portion for 5–10 min.
2. Immerse the membrane into 100 mL of the 0.026 M tin
chloride solution for 45 min.
3. Rinse the membrane as in step 1.
4. Immerse the membrane into 100 mL of the 0.035 M silver
nitrate solution for 7.5 min.
5. Rinse the membrane as in step 1.
6. Transfer the membrane to a 150 mL beaker containing the
gold plating solution, and keep the beaker in a water bath at
5
C for 4 h.
7. Immerse the membrane in a 100 mL beaker containing water
for 30 min.
8. Transfer the membrane to a 100 mL beaker containing a 25%
nitric acid solution for 1 h (see Note 10).
9. Rinse the membrane in water before letting it air-dry.
10. After drying, abrasively remove one of the membrane gold
surface films (top film in Fig. 1) with ethanol and a cottontip swab.
11. Attach a 10 cm strip of conductive copper tape to the remaining gold surface film (Fig. 1).
12. Electron micrographs of the membrane can be obtained to
determine the diameter and density of the gold microtubes
(Fig. 2).
3.2 Electrocompetent
Bacteria Preparation
(See Notes 5 and 7)
1. Grow a fresh E. coli culture overnight in 20 mL LB Broth in a
100 mL Erlenmeyer flask at 37
C while shaking (see Note 11).
2. Inoculate 100 mL of LB Broth with 1 mL of the fresh overnight culture in a 200 mL Erlenmeyer flask, and grow at 37
C
Fig. 1 Schematic illustration of a gold-microtube membrane. Dimensions are not
too scale
46
Juliette Experton et al.